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3920 Humidity Generator

The Model 3920 Low Humidity Generation System is a self-contained system capable of producing atmospheres of known humidity using the fundamental “two-pressure” principle. This system is capable of continuously supplying frost point, dew point, parts per million, relative humidity and other calculated values for instrument calibration and evaluation as well as for precision environmental testing. This system will automatically generate manually entered humidity as well as user created multipoint profiles. Visual indications of system status are displayed in real time on the computer monitor.


  • Traceable to SI 1
  • High Flow Capability of 10 L/min
  • Based on NIST Proven “Two-Pressure” Principle
  • HumiCalc® with Uncertainty Mathematical Engine
  • ControLog® Embedded Automation Software
  • Generate: Frost Point, Dew Point, PPM, %RH
  • Calculated Real-Time Uncertainty
  • Multi-point Touch LCD
  • Additional Keyboard Interface
  • Calculated Water Capacity to Indicate Water Usage

Model 3920 Automated Low Humidity Generator.

Key Specifications


Frost Point Temperature Range: –95 to 0.01 °C
Dew Point Temperature Range: –50 to 10 °C
Parts Per Million Range: 0.04 to 12300 PPMv
Relative Humidity Range: 0.00003% to ~50%
Temperature Specification: 0.027 °C
Saturation Temperature Range: 3 –80 to 12 °C
Saturation Temperature Control Stability: 4 0.008 °C
Saturation Temperature Cooling Rate: from 12 to –80 °C 0.33 °C per Minute (average)
Saturation Temperature Heating Rate: from –80 to 12 °C 0.33 °C per Minute (average)
Test Temperature Range (measured): 0 to 50 °C
Saturation Pressure Range: ~Ambient to 250 psiA
Saturation Pressure Specification: 0.02% of full scale
Test Pressure Range (measured): Ambient to 50 psiA
Test Pressure Specification: 0.02% of full scale
Gas Type: Gaseous Nitrogen
Supply Pressure Range: 80 to 300 psiG
Supply Pressure Specification: ±1 psiG
Gas Flow Rate Range: 0.5 to 10 SLPM
Gas Flow Rate Resolution: 0.2 SLPM
Gas Flow Rate Specification: 2% of full scale
Display Resolution: 0.001
Refrigeration: 1/3 HP R-134A & 1/3 HP R-23 in cascade
Heating: Stainless Steel Immersion
Test Port: 1/4 Inch Swagelok VCR®
Physical Dimensions: 37.9″ H x 23″ W x 34.9″ D (965mm x 585mm x 889mm)

Typical Applications

Chilled Mirror Hygrometers: Connecting the generator output to a chilled mirror hygrometer allows the user to verify the mirror temperature measurement accuracy; perform operational checks on the hygrometer components; determine whether the hygrometer is controlling the mirror in the liquid phase or ice phase when operating below 0 °C; determine if the hygrometer is correctly calculating other humidity parameters; determine hygrometer repeatability, stability, and drift characteristics.

Humidity Sensors and Electrolytic Hygrometers: Connect the generator output to a electrolytic hygrometer, sampling system, special fixtures, or sensors allows the user to calibrate and/or characterize humidity sensitivity; perform operational checks such as the sensing systems capability to correctly calculate and display other humidity parameters; determine repeatability, stability, hysteresis, and drift characteristics of various humidity sensing systems.

Environmental Testing: The 3920 can serve as a test bed for evaluation and R&D of humidity sensors, humidity sensing systems, and humidity sensitive products, e.g., polymers, composites, film, magnetic medium, pharmaceuticals, soil hydrology, consumables, electronics, optics, etc.